@ ProgramNode (location: (1,0)-(1,22))
├── locals: []
└── statements:
    @ StatementsNode (location: (1,0)-(1,22))
    └── body: (length: 1)
        └── @ CallNode (location: (1,0)-(1,22))
            ├── receiver: ∅
            ├── call_operator_loc: ∅
            ├── message_loc: (1,0)-(1,1) = "a"
            ├── opening_loc: ∅
            ├── arguments:
            │   @ ArgumentsNode (location: (1,2)-(1,13))
            │   ├── arguments: (length: 1)
            │   │   └── @ LambdaNode (location: (1,2)-(1,13))
            │   │       ├── locals: []
            │   │       ├── operator_loc: (1,2)-(1,4) = "->"
            │   │       ├── opening_loc: (1,5)-(1,7) = "do"
            │   │       ├── closing_loc: (1,10)-(1,13) = "end"
            │   │       ├── parameters: ∅
            │   │       └── body:
            │   │           @ StatementsNode (location: (1,8)-(1,9))
            │   │           └── body: (length: 1)
            │   │               └── @ IntegerNode (location: (1,8)-(1,9))
            │   │                   └── flags: decimal
            │   └── flags: ∅
            ├── closing_loc: ∅
            ├── block:
            │   @ BlockNode (location: (1,14)-(1,22))
            │   ├── locals: []
            │   ├── parameters: ∅
            │   ├── body:
            │   │   @ StatementsNode (location: (1,17)-(1,18))
            │   │   └── body: (length: 1)
            │   │       └── @ IntegerNode (location: (1,17)-(1,18))
            │   │           └── flags: decimal
            │   ├── opening_loc: (1,14)-(1,16) = "do"
            │   └── closing_loc: (1,19)-(1,22) = "end"
            ├── flags: ∅
            └── name: :a
